Mitral Valve disease is the most common type of heart disease in small dogs and is especially common in the Cavalier King Charles Spaniel, Toy and Miniature Poodle, Maltese Terrier and Chihuahua.
The valves in a normal heart close tightly to only allow blood to flow in one direction. Diseased valves will leak, allowing blood to flow backwards or regurgitate, which may be heard as a heart murmur. Leaky valves change the blood flow dynamics and internal blood pressure in the heart, often causing it to enlarge, which is seen on Xray.
Because the leaky heart valve allows blood to flow backwards, the pumping of the heart becomes less efficient and over time will lead to congestive heart failure. This may take a few months, or it may take several years.
Initially the dog attempts to cope by retaining fluid to increase blood volume. This fluid can gather in the lungs, causing decreased oxygen transfer and a cough.
Patients are often prescribed diuretics (eg frusemide) to reabsorb this fluid, and may be prescribed other medications such as Vetmedin or Fortekor to improve quality of life and extend survival times. Some patients require fluid to be drained, or may require oxygen therapy.
Monitoring your pet for a persistent cough or an increased resting respiratory rate at home is the best way to monitor their heart health in between their regular veterinary check ups.